Orthodontic bracket

ABSTRACT

Orthodontic bracket comprising a body ( 1 ) having a mesiodistal slot ( 10 ), a base ( 11 ), and a plurality of tie wings ( 12, 120 ) mainly developed along an occlusal-gingival direction, said tie wings being two-by-two on opposite sides in relation to said slot ( 10 ) and partially emerging over a labial side (L) of said body ( 1 ), wherein said slot ( 10 ) is apt to receive an archwire ( 2 ), wherein said tie wings ( 12, 120 ) protrude externally from the body ( 1 ) and towards the base ( 11 ), feature a curved surface ( 121 ) whose concavity is turned towards the same base ( 1 ) and constitute a support means for an element ( 3 ) apt to prevent the archwire ( 2 ) from coming out of the slot ( 10 ). That said element ( 3 ) features a planar portion intended to slide above, and parallel to, the labial side (L) of the body ( 1 ) and a flexible and elastic arm ( 33 ) having a portion ( 34 ) which is securable to the said surface ( 121 ) of two tie wings ( 12 ) resulting on the same side in relation to the slot ( 10 ). The said portion ( 34 ) of the flexible arm ( 33 ) moves along a curved path corresponding to the profile of the lower side (LT) of the said tie wings ( 12 ) while the planar portion of the said element ( 3 ) slides above the labial side (L) of the bracket body ( 1 ).

DESCRIPTION

The present invention relates to an orthodontic bracket.

In particular, the present invention relates to an orthodontic bracketof the “self-ligating” type.

It is known that, in orthodontics, use of orthodontic brackets cementedto the teeth of a dental arch is widely diffused. Such brackets,comprise a transverse slot crossed by a suitably shaped metallicarchwire which, due to its elasticity properties, transmits to the teetha set of forces which determine their movement according to apredetermined scheme, to obtain a more correct functional, biologicaland aesthetical positioning of the teeth. Examples of orthodonticbrackets are described in EP 876801, U.S. Pat. No. 5,622,494 and U.S.Pat. No. 5,326,259.

To prevent the archwire coming out of the bracket's slots, i.e. to holdthe archwire within the slots of the brackets, a ligating device,commonly called “ligature”, is applied to each bracket. In its simplestform, such a ligating device is an elastic ring.

Referring to “self-ligating” brackets, the ligating device is generallyconstituted by a mobile element which is connected to the bracket's bodyso that it can assume a slot opening position, to allow positioning ofthe archwire inside the slot, and a slot closing position, so that theslot is closed by the mobile element and the archwire cannot come out ofthe slot.

Generally speaking, such a mobile element is connected to the bracket'sbody so that it can rotate in relation to the latter, the opening andclosing of the slot being obtained by rotating the mobile element, or itcan be connected to the bracket's body so that it can slide over thelabial side of the bracket, the opening and closing of the slot beingobtained by moving the mobile element along an occlusal-gingivaldirection.

Examples of “self-ligating” orthodontic brackets wherein theaforementioned mobile element can rotate in relation to the bracket'sbody are disclosed in US20050266368, US20050244775, US20020110772 andU.S. Pat. No. 6,485,299.

Examples of “self-ligating” orthodontic brackets in which the elementwhich opens or closes the slot can slide over the bracket's labial sideare described in U.S. Pat. No. 5,322,435, US20050239012, US20060051721,U.S. Pat. No. 2,549,528 and US20060177790.

U.S. Pat. No. 5,711,666 discloses an orthodontic bracket comprising abracket body with a mesial distal extending arch wire slot and aligating latch spring member having the form of a thin flat metal strip.The spring member comprises, along its length, an anchor portionanchored in the bracket body, a flexing portion in which the majority ofthe flexing takes place, a ligating portion that closes the slot mouthand engages any arch wire therein, and a latching portion by which thespring member is latched to the bracket body. The spring membercomprises a biasing portion between the flexing and ligating portions atthe slot occlusal surface, or between the ligating and latching portionsat the slot gingival surface, this biasing portion being convex towardthe slot lingual wall and protruding into the slot to press the archwire into the respective slot wall junction for more precise control.The bracket body is made as two mirror image parts which are laserwelded together and between which the spring member is mounted. Thelatches between the spring member and the bracket body comprise notchesin the spring edges that are engaged by latch sears on the body, and twolabially lingually spaced sears are provided. The spring member is madeof a nickel titanium shape memory alloy. The bracket body has two pairsof tie wings for reception of an external ligature between which thespring member is disposed.

Drawbacks derive from the “self-ligating” orthodontic brackets commonlyavailable on the market, both for the cumbersome presence of the mobileelement, and for the high production costs which are due to the verycomplex realization and assemblage of the single parts. Furtherdrawbacks derive from the difficult use of such known brackets duringorthodontic therapy.

The present invention relates to an orthodontic bracket of the typecomprising a slot opening/closing mobile element which can slide overthe labial side of the bracket and it aims at simplifying the productionof this type of bracket and, at the same time, at reducing its cost andsize, increasing its reliability and safety and simplifying its use.

This result has been achieved, according to the invention, by adoptingthe idea of making an orthodontic bracket having the characteristicsdisclosed in claim 1. Further characteristics of the present inventionare dealt with in the dependent claims.

Thanks to the present invention, it is possible to realize a“self-ligating” orthodontic bracket which, with respect to the knownself-ligating orthodontic brackets, is cheaper, more compact, morereliable, more versatile, safer and easier to make.

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. In the appendeddrawings:

FIG. 1 shows a rear view of the body of an orthodontic bracket accordingto the present invention;

FIG. 2 is a perspective view of the bracket's body shown in FIG. 1;

FIG. 3 is a perspective view of the element destined to open/close theslot featured by the body of the bracket shown in FIGS. 1 and 2;

FIG. 4 shows an orthodontic bracket according to the present invention,the slot being open or accessible;

FIG. 5 shows the same orthodontic bracket of FIG. 4 but the slot isclosed;

FIGS. 6A-6C are three plan views relating to different positions of themobile element moving from the open to the closed slot position;

FIGS. 7A-7C are three side views, with partially sectioned parts,relating to different positions of the mobile element moving from theopen to the closed slot position as in FIGS. 6A-6C;

FIGS. 8A-8C are three plan views relating to different positions of themobile element moving from the closed to the open slot position;

FIGS. 9A-9C are three side views, with partially sectioned parts,relating to different positions of the mobile element moving from theopen to the closed slot position as in FIGS. 8A-8C;

FIGS. 10A and 10B schematically show the present orthodontic bracketapplied to a tooth and the use of a tool while the mobile element ismoved from the open to the closed slot position;

FIG. 11 is a diagram showing the positions assumed by the appendix (34)during the slot closing step.

Reduced to its basic structure and reference being made to the appendeddrawings, an orthodontic bracket according to the present inventioncomprises a body (1) having a slot (10) along a mesiodistal direction, abase (11) through which the bracket is bonded to a tooth (D) of thedental arch to be treated (for example, bonded to the vestibular side ofthe crown), and a plurality of tie wings (12, 120) which extend along anocclusal-gingival direction on opposite sides of the slot (10) and arepartially emerging above the labial side (L) of the body (1). Inside theslot (10), an archwire (2) can be positioned. For example, the archwire(2) can be made of a shape-memory type Ni—Ti alloy and it can have acircular cross section. The tie wings (12, 120) project externally fromthe bracket and towards the base (11), feature a curved surface(121)—which in jargon is called “underwing”—whose concavity is turnedtowards the base (11), and constitute supporting parts for an elementapt to hold the archwire (2) inside the slot (10).

The base (11) is bonded to the desired tooth by means of an orthodonticadhesive or cement.

The step of bonding the bracket to the tooth, as well as the structure,the positioning and the function of the archwire (2), i.e. theinteraction between the archwire, the bracket and the tooth, are knownto everyone skilled in the art and, therefore, they are not described infurther details.

The present bracket comprises an element (3) connected to the body (1)so that it can slide along an occlusal-gingival direction above thelabial side of the same body. Said element is destined to obtaincovering and, respectively, opening of the underlying slot (10).

In other words, said element (3) is utilized to open or close the slot(10), that is, to allow access to the slot or to hold the archwire (2)inside it.

According to the example shown in the appended drawings, said tie wings(12, 120) are four in number and are positioned, two-by-two, on oppositesides with respect to the slot (10), i.e. they form a pair of occlusaltie wings (12) and a pair of gingival tie wings (120).

Furthermore, said tie wings (12, 120) have an external occlusal-gingivalside (12A) and an inner occlusal-gingival side (12B) and they feature agroove (12S) which, as further described below, acts as a guide for theelement (3).

Reference being made to the example shown in the appended drawings, allsaid grooves (12S) are on the labial side of the body (1), arerectilinear and each of them has the same length of the respective tiewing.

Furthermore, since said tie wings (12, 120) are two-by-two on oppositesides of the slot (10), each of the said grooves (12S) is aligned with acorresponding groove (12S) resulting on the opposite side in relation tothe slot (10).

Said body (1) is provided with an appendix (13) orthogonally emergingfrom its labial side (L), on the inner side (12B) of each of saidocclusal tie wings (12).

The said appendixes (13) act, as further described below, as a means forstopping the element (3) when the latter is moved to open the slot (10).

The said element (3) is made of a thin plate, for example of stainlesssteel, having an anterior edge (30), a rear zone (31), and two sides(32) destined to slide within the guides constituted by the said grooves(12S).

The said element (3) has an elastically flexible arm (33) centrallypositioned between the said sides (32) so as to protrude with respect tothe rear ends (320) of the sides (32), and is provided with a rearappendix (34) which is orthogonally oriented with respect to the samearm, i.e. it is mainly developed along a mesio-distal direction. Inother words, when seen in plan view, the said element (3) is “E”-shaped,with an elastically flexible central portion (33) protruding beyond theothers (32) and provided with a transverse appendix (34) on its freeend. Yet in other words, the said element (3) has, on the side oppositeto its anterior edge (30), i.e. on its rear portion, a flexible andelastic part (33) which is mainly developed along an occlusal-gingivaldirection, protrudes beyond the ends (320) of its sides (32) and has atransverse appendix (34). In practice, the central arm (33) of the“E”-shaped element (3) is longer than the others (32).

The said sides (32) of the element (3) are united to the central arm(33)—on the end (330) of the arm (33) which is opposite the end providedwith the transverse appendix (34)—by the same material which the element(3) is made of. In practice, the longitudinal edges (331) of the centralarm (33) are spaced from the inner edges (321) of the said sides (32),so that the central arm (33) can flex; furthermore, at the two sides ofthe said end (330) of the arm (33) there are two corresponding concavesurfaces (35), whose height is equal to the thickness of the element(3), and whose concavity is turned towards the rear part of the element(3), i.e. is turned towards the appendix (34) of the arm (33).

As further described below, when the slot (10) is open, i.e. when theelement (3) is moved backwards, each of the said surfaces (35) isintercepted by a respective appendix (13) of the body (1).

The length (x) of the aforementioned appendix (34) is greater than thedistance (y) between the inner sides (12B) of two tie wings (12)resulting on the same side in relation to the slot (10). For example,the said length (x) is 15÷40% greater than the said distance (y)(x=1.15÷1.40 y). Preferably, the said length (x) is less than thedistance between the external sides (12A) of two tie wings (12)resulting on the same side in relation to the slot (10).

According to the example shown in FIG. 3, the element (3) has a planarportion, which is delimited by the edges or sides (30), (32), (320) and(321), and the said flexible arm (33) is bent downwardly, so that theappendix (34) of the arm (33) results lower in relation to the planarportion.

The said planar portion of the element (3) provides the veryopening/closing of the slot (10) when it slides above the labial side(L) of the bracket body (1).

The orthodontic bracket disclosed above works as follows.

When the slot (10) is open, as shown in FIGS. 4, 6A, 7A and 10B, i.e.when the element (3) is moved backwards, the sides (32) of the element(3) are inside the grooves (12S) of the occlusal tie wings (12), thesaid surfaces (35) are in contact with the appendixes (13) of the body(1), and the appendix (34) of the arm (33) is spaced from the occlusaltie wings (12).

In order to close or cover the slot (10), the arm (33) is pushed forwardand is bent downward, as shown by the arrows in FIGS. 6A-7C, for exampleby making use of a tool (U) having a rod-shaped portion as shown inFIGS. 10A and 10B. In this way, the element (3) slides over the labialside (L) of the body (1), while the sides (32) of the same element slideinside the guides constituted by the grooves (12S) of both the, occlusaland gingival tie wings (12, 120), and the appendix (34) is positionedbeneath the occlusal tie wings (12) which, as said before, have aconcave portion (121) turned towards the base (11). In this position,due to the elasticity of the arm (33), the appendix (34) is pushedagainst the surfaces (121) of the tie wings (12), so that the element(3) is firmly locked in the slot (10) closing position.

As shown in FIG. 11, when the arm (33) is pushed forward and is bentdownward, the appendix (34) comes into contact with the external surfaceof the tie wings (12), then it follows a curved path corresponding tothe lower profile of the latter and, finally, it raises—due to theelasticity of the arm (33)—and comes into contact with the “under-wings”(121). In other words, when the arm (33) is pushed forward and is bentdownward the appendix (34) assumes the position (A), then the position(B) and, finally, the position (C). Positions (A) and (C) are higherthan position (B) in relation to the base (11). It is noted that thesides (32) of the element (3) move parallel to the labial side (L) ofthe body (1) while the appendix (34) provided by the arm (33) of thesame element (3) moves along a curved path. In fact, the said sides (32)slide inside the rectilinear grooves (12S) provided on the labial side(L) of the body (1) by the occlusal tie wings (12), while the appendix(34) moves along a curved path corresponding to the lower profile of thesame tie wings (12), i.e. corresponding to the profile of the lowerportion (LT) of the latter.

In order to open the slot (10), by making use of the same tool (U), itis sufficient to simply push on the anterior edge (31), as shown by thearrows in FIGS. 8A-9C, thus provoking the moving of the element (3)backwards and the disengagement of the appendix (34) from its contactwith the surfaces or “under-wings” (121) of the occlusal tie wings (12).

Although the above description and the accompanying drawings relate tosome embodiments of the invention, the invention is not limited thereto.One skilled in the art will understand that numerous variations andmodifications are possible without departing from the spirit and scopeof the invention defined by the following claims.

1. An orthodontic bracket comprising: a body having a mesiodistal slot,a base, and a plurality of tie wings mainly developed along anocclusal-gingival direction, said tie wings being two-by-two on oppositesides in relation to said slot and partially emerging over a labial sideof said body, wherein said slot is apt to receive an archwire, whereinsaid tie wings protrude externally from the body and towards the base,said tie wings comprising a curved surface whose concavity is turnedtowards the base and constitute a support means for an element apt toprevent the archwire from coming out of the slot, said elementcomprising a planar portion intended to slide above, and parallel to,the labial side of the body, said element comprising a flexible andelastic arm having a portion which is securable to said surface of twotie wings resulting on the same side in relation to the slot, saidsecuring portion of the flexible arm moving along a curved pathcorresponding to the profile of the lower side of said tie wings whilethe planar portion of said element slides above the labial side of thebracket body, and said tie wings comprising rectilinear grooves in whichtwo sides of said element can slide.
 2. An orthodontic bracket accordingto claim 1, wherein said portion of said arm is developed transversallyto the same arm.
 3. An orthodontic bracket according to claim 1, whereinsaid body comprises an appendix orthogonally emerging from its labialside, on the inner side of each of two occlusal tie wings.
 4. Anorthodontic bracket according to claim 3, wherein said appendixes arestopping means for the element when the element is moved to open theslot.
 5. An orthodontic bracket according to claim 1, wherein saidelement is made of a thin plate, with an anterior edge, a rear zone, andtwo sides intended to slide inside grooves provided by the tie wings. 6.An orthodontic bracket according to claim 1, wherein said sides areunited to the central arm, on the end of the arm which is opposite theend with the transverse appendix, by the same material of which theelement is made, the longitudinal edges of the central arm being spacedfrom the inner edges of said sides, so that the central arm can flex. 7.An orthodontic bracket according to claim 6, wherein at the two sides ofsaid end of the arm there are two corresponding concave surfaces, whoseconcavity is turned towards the rear part of the element, wherein saidconcavity of said concave surfaces is turned towards the said portion.8. An orthodontic bracket according to claim 5, wherein said sides areunited to the central arm, on the end of the arm which is opposite theend with the transverse appendix, by the same material of which theelement is made, the longitudinal edges of the central arm being spacedfrom the inner edges of said sides, so that the central arm can flex.